Cam grinding

ABSTRACT

Cam grinding apparatus comprising a frame adapted to be pivotally mounted between the headstock and tailstock of a grinding machine, workpiece holding means arranged on the frame to carry a cam workpiece to be ground with its axis parallel to but eccentric from the headstock-tailstock axis means to drive the workpiece holding means to rotate a workpiece carried therein, and master cam holding means associated with the workpiece holding means and arranged to carry a master cam in engagement with a guide surface whereby the frame pivots about its mounting to carry the workpiece towards or away from the grinding wheel of the machine in accordance with the master cam on rotation of the cam workpiece.

United States Patent 91 Naismith [451 Feb. 11, 1975 1 1 CAM GRINDING [211 App]. No.: 354,745

[30] Foreign Application Priority Data Primary Examiner0thell M. Simpson Attorney, Agent, or Firm-Karl W. Flocks 157] ABSTRACT Cam grinding apparatus comprising a frame adapted to be pivotally mounted between the headstock and tailstock of a grinding machine, workpiece holding means arranged on the frame to carry a cam workpiece to be ground with its axis parallel to but eccentric from the headstock-tailstock axis means to drive the workpiece holding means to rotate a workpiece carried therein, and master cam holding means associated with the workpiece holding means and arranged to carry a master cam in engagement with a guide surface whereby the frame pivots about its mounting to carry the workpiece towards or away from the grinding wheel of the machine in accordance with the master cam on rotation of the cam workpiece.

13 Claims, 3 Drawing Figures PATENTEDFEBI 1 1915 SHEET 1 OF 3 T NN r f C u m D S v I TH mmgnram 1 1975' SHEEI 2 OF 3 CAM GRINDING BACKGROUND. OF THE INVENTION This invention relates to apparatus for grinding cam surfaces and is particularly, but not exclusively concerned with apparatus for adapting a cylindrical grinding machine or a crank shaft grinding machine for the grinding of motor vehicle engine cam shafts.

In the re-conditioning of motor vehicle engines it is common practice to'regrind the crankshaft to re-form the various journals thereon. Consequently there are many crankshaft grinding machines of various types in use in the trade. At the same time it is often desirable to regrind the cam surfaces on the cam shaft of the engine, and this hasinvolved the use of expensive specialist machinery not commonly available in engine reconditioning workshops.

It is an object of the present invention to provide apparatus which can be used on a conventional crankshaft grinding machine, or on a conventional cylindrical grinding machine, to adapt either type of grinding machine for the grinding of the cam surface of a cam shaft.

SUMMARY OF THE INVENTION Accordingly the present invention provides cam grinding apparatus comprising a frame adapted to be pivotally mounted between the headstock and tailstock of a grinding machine, workpiece holding means arranged on the frame to carry a cam workpiece to be ground with its axis parallel to but eccentric from the headstock-tailstock axis, means to drive the workpiece holding mea'ns from the headstock to rotate a workpiece carried therein, and master cam holding means associated with the workpiece holding means and arranged to carry a master cam in engagement with a guide surface whereby the frame pivots about its mounting between the headstock and tailstock towards or away from the guiding wheel of the machine in accordance with the master cam on rotation of the cam workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS In order to promote a fuller understanding of the above, and other, aspects of the present invention, an embodiment will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 shows a schematic side elevation of the embodiment of the invention,

FIG. 2 shows a part cross-sectional view on the line IIII of FIG. 1, and

FIG. 3 shows a part cross-sectional view on the line Ill-III of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 of the drawings, there is shown in outline the headstock 5 and tailstock 6 of a conventional crankshaft grinding machine of known type per se in which the grinding wheel is carried on a pivotally mounted arm to achieve grinding wheel feed. An embodiment of the invention is shown mounted between the work centres of the headstock and tailstock and on the bed 7 of that grinding machine.

The cam grinding apparatus of this embodiment comprises a frame indicated generally at 10 comprising a headstock end plate 11 and tailstock end plate 12 respectively provided with shafts l3 and l4 by which the frame 10 is pivotally carried between the driven headstock 5 and the running tailstock 6 of the grinding machine. The shaft 13 is rotatably mounted and axially located by means of suitable precision taper roller bearings (not shown) in a support member 17 which is in turn adapted to locate on and be clamped on the bed 7 of thegrinding machine. The end plate 11 is mounted by means of suitable precision taper 'roller bearings (not shown) on the shaft 13, and is connected to the end plate 10 by means of an adjustable length member 19. A three jaw self-centring chuck 20 is carried on a shaft 21 which is mounted .in the end plate 11 by means of suitable precision taper roller bearings (not shown) and rotationally coupled to the shaft 13 by suitable drive means, preferably by a backlash free toothed belt or chain drive arrangement such as that indicated at 15. The end plate 12 is provided with a running centre 22 which is axially aligned with the chuck 20 so that a motor vehicle engine cam shaft such as that indicated at 23 may be carried between them.

Thus it can beseen that as the headstock 15 of the grinding machine rotates in operation of that machine, the cam shaft 23 carried between the chuck and centre will also be rotated. Further, it can be seen that as the frame assembly 10 pivots about the shaft 13 and the tailstock 6, the cam shaft will be carried towards and away from the grinding wheel (indicated in outline at 24) of the machine. In order to maintain engagement between the grinding wheel 24 and one of the cams on the cam shaft 23 the frame 10 is resiliently biassed to rotate about its supports in the appropriate direction by means of a spring device indicated generally at 25 arranged between a roller 16 on the headstock end plate 11 and a suitable portion of the support member 17.

The shaft 21 includes an extension behind the chuck 20 which is adapted to receive a master cam group 30 comprising master cams 30a, 30b, 30c, 30d. A second support member 31 is-provided to be carried on the bed 7 of the grinding machine and a guide member 32 is adjustably mounted on that support member 31 in such position that it bears against a chosen one 30a of the master cam group 30. The guide member 32 is adjustabl) mountedon the support 31 in order that it can be correctly aligned with its operative surface in register with the surface of the grinding wheel 24, whereby as the cam shaft 23 is rotated, the support frame 10 and the cam shaft 23 is rocked about the headstocktailstock axis towards and away from the grinding wheel 24 as dictated by the master cam 30a. This has the result that the grinding wheel 24 accurately reproduces on the cam shaft 23 the profile of the master cam The master cam group 30 is formed on a stub shaft 35. The stub shaft 35 is formed with a standard morse taper end to fit into a mating taper in the shaft 21 and a suitable angular locating key is provided in the stub shaft to fit into a corresponding slot in the shaft 21.

The chuck 20 is provided with suitable adaptors and a locating peg to pick up and locate the end flange or other drive arrangement which is provided on the cam shaft, to drive and angularly locate it in use in an engine. The chuck 20 is angularly adjustable on the shaft 21, a calibrated angular scale and pointer arrangement shown generally at 36 being provided between them.

Thus it can be seen that the master cam group 30 of which the cam 30a shown in use may for instance be an exhaust cam profile may be angularly aligned successively with each such exhaust cam on the cam shaft to be ground. The whole assembly is carried axially on the bed 7 of the grinding machine by moving that bed in the conventional manner to bring each cam of the cam shaft to be ground into engagement with the grinding wheel 24.

In the preferred arrangement the master cam group 30 comprises a group of master cams corresponding to and angularly related in accordance with the cams of at least two cylinders for a four cylinder engine and three cylinders for a six cylinder engine. In this way it can be seen that it is only necessary to change the angular setting of the cam shaft being ground relative to the master cam group once. In alternative arrangements a master cam on a stub shaft can be inserted in the shaft 21 for each cam to be ground, the angular relationship of that master cam on its stub shaft being in accordance with the requirements of the cam to be ground.

In a further arrangements a whole master cam shaft may be provided again eliminating the need for angular adjustment of the chuck 20. In this last arrangement a further support for the end of the master cam shaft remote from the shaft 21 is provided in the form of a suitable bracket and bearing.

As best seen in FIG. 2, the guide member 32 is pivotally mounted at the end of a slide member 39 which is slidably mounted in the support member 31 for movement in a direction transverse to the axis of the shaft 21. This movement is provided to compensate the wear and re-dressing of the grinding machine, particularly in the case of a grinding machine of the type where the grinding wheel spindle is carried on a pivotally mounted arm to provide grinding feed as in the case of one widely used crankshaft grinding machine.

In the case of a pivotally mounted arm feed, the centre height of the wheel spindle above the bed 7 of the machine varies with feed, and as the grinding wheel is progressively dressed down in size, unless compensation is made for this the cam profile ground will become incorrect with wheel wear. This is illustrated in FIG. 2, where the grinding wheel 24 is shown carried on a pivotally mounted arm for feed, the arm pivoting about an axis 40 with the axis of the wheel moving on an are 41. It can be seen that if that part of the arc 42 on which the axis of the cam shaft and shaft 21 moves as the frame swings about the headstock-tailstock axis in accordance with the master cam, is chosen correctly then in nominal terms the height of the wheel axis above the bed 7 can be maintained the same as the height of the cam shaft axis above the bed. When this is done, the profile ground on the cam shaft will be in accordance with and correctly angularly related to that of the master cam.

The slide member 39 is adjustable in the support 17 by means of a calibrated collar 43, which is screw threaded onthe slide member and axially trapped in the support 17.

The guide member 32 can be caused to pivot about its mounting on the slide member 39 by means of a push rod 44 passing through the slide member and a knurled knob 45 which is screw threaded in the end of the slide member. A scale calibrated in degrees is provided on the slide member so that the angle made between the operative face 46 of the guide member that engages a master cam and the line of contact between the grinding wheel and the cam shaft being ground, may be established. It can be seen that this angle is directly related to the angular relationship of a master cam and the corresponding profile which is reproduced on a cam shaft being ground, and therefore the adjustment of the knob 45 to set a particular angle for the guide member 32 may achieve and advance or retardation of the cam profile ground on a cam shaft at will.

As best seen in FIG. 3, a catch mechanism 50 is provided to retain the frame 10 in an inoperative position with the cam shaft workpiece clear of the grinding wheel. The catch mechanism which is showm in the released condition comprises a catch 51 pivotally mounted in the support member 17 and formed with a notch 52 arranged to receive and retain a peg 53 on the frame member 11 to hold it in the inoperative position.

If the apparatus of the invention is to be used with a grinding machine in which there is a linear feed for the grinding wheel, either of the wheel relative to the bed or the bed relative to the wheel, then the centre of the grinding wheel always lies on a line which usually passes through the axis between the headstock and tailstock. In these circumstances, while the above embodiment with the adjustable guide surface 32 may be used with suitable adjustment of that guide surface, is is preferable to use a modified embodiment. In the modified embodiment the shaft 13 about which the frame 10 pivots is lowered to bring the axis of the cam work piece into nominal coincidence with the headstock-tailstock axis, with a suitable drive being provided to the lowered shaft 13 from a further shaft arranged to be coupled to the headstock. A suitable arrangement for the lowering of the pivot axis at the tailstock end is also provided. Again if desired in either arrangement a separate drive may be provided on the frame 10 for the work piece holding means independent of the headstock of the grinding machine.

It is to be noted that the second support member 31 may be positioned on the bed 7 of the grinding machine the other side of the support member 17. In this arrangement, the guide surface 32 may be brought to bear on a cam surface on the cam shaft work piece so that that surface may be reproduced elsewhere on the cam shaft. In this way also master cams or cam groups may be ground.

I Claim:

1. For use with a grinding machine having a bed, a grinding wheel having a rotation axis, a headstock and a tailstock with a headstock-tailstock axis; a cam grinding attachment comprising a frame having means for pivotal mounting between the headstock and tailstock of the grinding machine, workpiece holding means carried by the frame having means to carry a cam workhaving a guide surface for engagement with a master cam, adjustment means coupled with the guide member whereby the guide member may be pivotally adjusted so that the guide surface registers with the grinding wheel surface in a plane joining the axes of rotation of the grinding wheel and a cam workpiece whereby in use the frame pivots about its mounting means to carry the workpiece towards or away from the grinding wheel in accordance with the master cam on rotation of the cam workpiece.

2. Apparatus as claimed in claim 1 including a second support member for location on the bed of the grinding machine, a first shaft having one end rotatably mounted in the second support and another end having means for rotatable mounting in said headstock of the grinding apparatus, said first shaft being coupled to be driven from the headstock of the grinding machine, wherein said frame is pivotally mounted about said first shaft and said workpiece holding means is coupled to be driven from said first shaft.

3. Apparatus as claimed in claim 2 wherein said frame comprises a headstock end plate pivotally mounted about said first shaft, a tailstock end plate having means for rotatable mounting in the tailstock of the grinding machine, the two end plates being rigidly connected by means of an adjustable length member.

4. Apparatus as claimed in claim 3, wherein said workpiece holding means includes a chuck carried on one end of a second shaft which is rotatably mounted in said headstock end plate.

5. Apparatus as claimed in claim 4, wherein said second shaft is coupled with the first shaft by means of a belt or chain drive.

, 6. Apparatus as claimed in claim 4, wherein said second shaft is extended at the other end to form the master cam holding means to receive said master cam.

7. Apparatus as claimed in claim 1, including a plurality of master cams carried by said cam holding means.

8. Apparatus as claimed in claim 1, wherein first support member has mounting means for mounting it on the bed of the grinding machine.

9. Apparatus as claimed in claim 1 including lead screw means coupled with said first support member whereby said first support member may be moved along the bed of the grinding machine relative to said cam holding means to align the guide surface with a chosen one of a group of cams carried in said cam holding means.

10. Apparatus as claimed in claim 1, wherein said guide member is pivotally carried on a slide member which is adjustably movable in said first support member in a direction transverse to the axis of the master cam holding means.

11. Apparatus as claimed in claim 1, wherein said workpiece holding means includes calibrated means whereby the angular orientation between a workpiece held therein and said master cam may be adjusted.

12. Apparatus as claimed in claim 1, wherein said frame is resiliently biassed about its pivot axis to carry a cam workpiece thereon into engagement with the grinding wheel of the grinding machine.

13. Apparatus as claimed in claim 1 wherein catch means is provided to retain the frame in an inoperative position with a cam workpiece thereon clear of the grinding wheel of the grinding machine. 

1. For use with a grinding machine having a bed, a grinding wheel having a rotation axis, a headstock and a tailstock with a headstock-tailstock axis; a cam grinding attachment comprising a frame having means for pivotal mounting between the headstock and tailstock of the grinding machine, workpiece holding means carried by the frame having means to carry a cam workpiece to be ground with its axis parallel to but eccentric from the headstock-tailstock axis, drive means coupled to the workpiece holding means to provide substantially continuous rotation of a workpiece carried therein, a master cam holding means coupled with the workpiece holding means having an axis coaxial with the axis of the workpiece and having means to carry a master cam, a first support member, a guide member pivotally mounted on the support member for pivotal movement about an axis parallel to the axis of the master cam holding means but eccentric therefrom and having a guide surface for engagement with a master cam, adjustment means coupled with the guide member whereby the guide member may be pivotally adjusted so that the guide surface registers with the grinding wheel surface in a plane joining the axes of rotation of the grinding wheel and a cam workpiece whereby in use the frame pivots about its mounting means to carry the workpiece towards or away from the grinding wheel in accordance with the master cam on rotation of the cam workpiece.
 2. Apparatus as claimed in claim 1 including a second support member for location on the bed of the grinding machine, a first shaft having one end rotatably mounted in the second support and another end having means for rotatable mounting in said headstock of the grinding apparatus, said first shaft being coupled to be driven from the headstock of the grinding machine, wherein said frame is pivotally mounted about said first shaft and said workpiece holding means is coupled to be driven from said first shaft.
 3. Apparatus as claimed in claim 2 wherein said frame comprises a headstOck end plate pivotally mounted about said first shaft, a tailstock end plate having means for rotatable mounting in the tailstock of the grinding machine, the two end plates being rigidly connected by means of an adjustable length member.
 4. Apparatus as claimed in claim 3, wherein said workpiece holding means includes a chuck carried on one end of a second shaft which is rotatably mounted in said headstock end plate.
 5. Apparatus as claimed in claim 4, wherein said second shaft is coupled with the first shaft by means of a belt or chain drive.
 6. Apparatus as claimed in claim 4, wherein said second shaft is extended at the other end to form the master cam holding means to receive said master cam.
 7. Apparatus as claimed in claim 1, including a plurality of master cams carried by said cam holding means.
 8. Apparatus as claimed in claim 1, wherein first support member has mounting means for mounting it on the bed of the grinding machine.
 9. Apparatus as claimed in claim 1 including lead screw means coupled with said first support member whereby said first support member may be moved along the bed of the grinding machine relative to said cam holding means to align the guide surface with a chosen one of a group of cams carried in said cam holding means.
 10. Apparatus as claimed in claim 1, wherein said guide member is pivotally carried on a slide member which is adjustably movable in said first support member in a direction transverse to the axis of the master cam holding means.
 11. Apparatus as claimed in claim 1, wherein said workpiece holding means includes calibrated means whereby the angular orientation between a workpiece held therein and said master cam may be adjusted.
 12. Apparatus as claimed in claim 1, wherein said frame is resiliently biassed about its pivot axis to carry a cam workpiece thereon into engagement with the grinding wheel of the grinding machine.
 13. Apparatus as claimed in claim 1 wherein catch means is provided to retain the frame in an inoperative position with a cam workpiece thereon clear of the grinding wheel of the grinding machine. 